A computer monitor may be the last
peripheral on your wish list. After all, an extra color or even
black-and-white TV set works fine with most home computers. But lower
monitor prices, new accessories, and combination TV/ monitors are
quickly changing the picture for the better.Until
about a year ago, most computer owners didn't have to spend too much
time deliberating over which computer display to buy. Color monitors
cost more than brandnew color TV sets, so most people didn't buy a
special display for their computers-they just used TV sets. Others used
spare black-and-white sets, even for computers with color graphics.
But recently the options have widened. Thanks partly
to Commodore's unexpected success with the 1701/1702 color monitors,
manufacturers have spotted a niche in the market that was not being
exploited, and now they're scrambling to fill it. In addition, TV
manufacturers are finally realizing that TVs are being used for a lot
more than just watching TV - people are plugging in home computers,
videogame machines, videocassette recorders, stereo sound systems, and
videodisc players.
The result is a wider variety of affordable color
and monochrome monitors compatible with nearly all home computers, plus
a new generation of combination TV/monitors equipped with an array of
video and audio input/output jacks. There is even a combination TV/
composite color/RGB color/ monochrome monitor that sells for not much
more than an old-fashioned color TV. And new low-priced accessories let
you turn existing computer monitors into TV/monitors.
Since the display device is the most-used peripheral
in a computer system (you're staring at the screen for up to hours on
end), it's time to take a fresh look at what's happening in computer
video.

Unlike
many peripherals, a monitor will probably be compatible with a
different computer if you ever upgrade your system. So it makes sense
to take special care when selecting one. It's also important to
understand all the technical terms and specifications (see the
accompanying article, "RGB Versus Composite Video").Resolution refers
to how sharply the screen can display an image. The greater the
resolution, the better. For several technical reasons, ordinary TV sets
have trouble displaying computer text. That's why all home computers
designed to work with TVs limit the width of their displays to no more
than 40 characters. An 80column display-standard on business
computers-would be too fuzzy to read comfortably on the average TV.
You can quickly convert most home computers for
80-column text by plugging in a video adapter board or by running a
special program. But to read the screen without suffering headaches,
usually you must buy a monochrome (noncolor)
monitor. Monochrome monitor, are available with black-and-white, green,
and amber displays (some studies suggest tha green and amber displays
are easier on your eyes). Why must you buy a monochrome monitor?
Because
even the most common type of color monitor-called a composite color monitor-has
problems displaing 80 columns of text. People '' who spend lots of
time staring at the screen, particularly writers and programmers,
need the sharpest resolution possible to avoid eye fatigue.
Until recently, the only other alternative was to
buy a much more expensive type of color monitor, an RGB (red-green-blue) monitor. But
few home computers have RGB - compatible outputs, though sometimes one
can be added at extra cost.
Fortunately, improved technology has drastically cut
the price of RGB monitors and has made it possible for some composite
color monitors to display sharp 80-column text as well as graphics. For
instance, Teknika Electronics makes a 13-inch color monitor, the MJ-10,
that has both composite and separated
video, just like a Commodore 1701/1702. The separated video
mode-which separates certain components in the video signal-can produce
an acceptably sharp 80-column display on computers with separated video
outputs. Although the only computers with such outputs are the
Commodore 64, Plus/4, Commodore 16, and Atari 800, the Teknika MJ-10
also works in regular composite mode with the IBM PC and PCjr, Apple,
Atari XLs, and Commodore VIC-20. The suggested retail price is $299.
Teknika's MJ-22 is also a 13-inch color monitor, but
is switchable between composite video and RGB. Retailing at $439.95, it
is several hundred dollars less than what RGB monitors used to cost and
is compatible with the IBM PC and PCjr, Apple, Atari, Commodore, and
Texas Instruments computers. Sakata Corporation, a Japanese electronics
manufacturer, also makes a composite video/RGB monitor for under $500,
the SC-150.

Other
companies are marketing color monitors with multiple display modes,
too. Perhaps the most versatile to date is the Sears Total Video
System. At the push of a button, you can use its 13-inch screen as a
composite color monitor, RGB color monitor, green-screen monochrome
monitor, or as an ordinary TV set. It even has a button that shrinks
the screen image slightly to tighten the dot patterns for sharper text
in RGB mode. The RGB jacks are directly compatible with the IBM PCjr,
and an adapter makes it work with the PC, too. The monitor is also
compatible with virtually all other microcomputers. Its suggested
retail price is $349 - about half as much as what comparable RGB-only
monitors used to sell for.
General Electric has two multifunction models. Like
the Sears Total Video System, the 13-inch GE Computer Monitor/ TV has
an input jack that allows a composite color video signal to bypass the
TV's tuner circuits, resulting in a cleaner display. GE also offers a
12-inch black-and-white TV/monitor. (GE has no suggested retail prices;
check your local dealer.)
Manufacturers are beginning to equip their TVs with
video and audio input jacks because they also make it easier to
connect other video devices, such as videocassette recorders. Watch for
the next generation of TVs to have a complete set of input/output jacks
as a standard feature, just like stereo receivers. These jacks add
relatively little to the manufacturing cost of a TV and help eliminate
tangles of wires and switchboxes. They also make the TVs a good buy for
families who don't use their computer often enough to justify the cost
of a dedicated computer monitor.
If you already have a computer monitor, and you live
in a household where the arrival of the weekly TV viewing schedule is a
springboard for major debates, new add-on tuners can convert your
existing monitor into a combination TV/monitor, too. One example is the
Cardco Monitor Tuner, which turns any composite color or monochrome
monitor into a TV for $99.95. It has an audio output (which can be
connected to a stereo system), a computer/TV switch, and a
cable/antenna input. A slightly more expensive model has remote control.

Now you can watch TV while waiting for programs to load: Cardco's
Monitor Tuner converts any composite computer monitor into a
combination TV/monitor.

RGB Versus Composite
VideoOttis
Cowper, Technical Editor

Color video is similar in principle to monochrome video, the original
black-and-white television technology. In a monochrome monitor (or
black-and-white TV), the image is produced by spraying the screen with
a beam of electrons from a hot filament (called a gun) at the back of
the picture tube. The screen has a special phosphorescent coating that
glows wherever the electrons strike. By carefully aiming the gun to
illuminate certain phosphor dots on the tube, detailed images can be
painted on the screen. Thus, four separate signals are required to
create a monochrome video display: one to control which dots are
illuminated, one to control the intensity (brightness) of the display,
and one each for synchronizing the vertical and horizontal targeting of
the beam.
The challenge in making the leap from monochrome to
multicolor was
to devise a simple method of generating all the subtle hues the human
eye can distinguish. It's possible to make phosphors that will glow a
particular color; witness the black-and-white, green, and amber
monochrome monitor screens now available. But a color screen would seem
to require thousands of different phosphors for all the desired colors.
Fortunately, the process isn't quite that complicated.
According to optical physics, all visible colors can
be created by
mixing just three primary colors
in various proportions. For color
video, the primary colors are red, green, and blue. Any other colors
you see on a computer display or color TV are combinations of these
three.
On a monochrome display, each of the tiny spots that
make up a
figure consists of a single glowing dot of phosphor. On a color
display, three closely spaced phosphor dots are required for each
point-one red, one green, and one blue. As a result, the smallest
element of any feature on the color display will be at least three
times larger than the smallest element on a monochrome screen. This is
one reason why color displays tend to be less sharp-to have lower resolution-than
monochrome displays.
A color display, then, requires six separate
signals: one each for
red, green, and blue dots (replacing the single signal required for
monochrome dots), plus the intensity, horizontal, and vertical control
and synchronization signals. The differences between composite video
and RGB (red-green-blue)
color
displays have to do with how these
signals are sent to and processed by the monitor.
Composite video is the most common system because
the circuitry is
quite similar to that for a color TV, so the components are readily
available and relatively inexpensive. As the name composite video
implies, these monitors receive and process a composite signal-one in
which all the separate signal elements for the display are combined
into a single signal. The monitor divides the composite signal from the
computer into its various parts to target the electron gun and
illuminate the proper colored phosphor dots.
In an RGB color monitor, each of the different
phosphor colors is
illuminated by a separate gun-hence the name RGB. Rather than sending
the monitor a composite signal, the computer sends each signal
separately, and separate circuits in the monitor target each of the
three electron guns. The colors are mixed more precisely and appear
much sharper. The disadvantage is that the more specialized circuitry
costs more.
At present, there is also one intermediate step
between composite
video and RGB. The Commodore 64, Plus/4, Commodore 16, and Atari 800
computers have video outputs that can separate the color portions of
the composite signal from the intensity portion. The two signals are
referred to as chroma (short
for chrominance, or color)
and luma (for luminance, or
brightness). The Commodore 1701/1702 color monitors can
accept these separated signals in addition to standard composite video.
The chroma/luma separation yields a picture that, while still less
sharp than RGB, is a distinct improvement over standard composite
displays.
The choice between composite and RGB displays may be
quite simple.
If you have a computer that is designed to provide only composite video
output-as is the case with most home computers-then the higher quality
of an RGB display is unavailable to you. We know of no adapters to
break a composite signal into its RGB components. If, however, you have
an IBM PC with a color/graphics adapter, an IBM PCjr, or perhaps an
Apple or Atari 800 with an RGB adapter card, you can compare the two
systems and decide if the superior quality of RGB is worth the higher
cost.

You can also use a videocassette recorder to convert
a monitor into a TV. Just run a cable from the VCR's video output jack
to the monitor's video input jack, and then use the VCR's own tuner.
Another new accessory turns RGB color monitors into
very sharp monochrome monitors. The GreenSwitch, from Future Products,
changes the screen color to green-on-black. The switch has an
IBM - compatible, nine-pin D-connector, installs easily with a
screwdriver, and retails for $49.95.

Sakata
Corporation caused a bit of a stir with a new monitor at last fall's
COMDEX trade show in Las Vegas. Publicity Director Sandy Rodkin, of
Rodkin & Associates, recalls seeing a cable TV crew pass by their
display, stop, and stare. "Why is that picture better?" they asked.
The monitor they were looking at was a new
flat-screen model, the Sakata SFS-200. It has a color liquid crystal
display (LCD) that is not only extremely sharp, but more portable than
a conventional cathode ray tube (CRT). Small monochrome LCD screens
already are common on portable lap computers such as the TRS-80 Model
100. Large color flat screens are still relatively expensive and slow
(the SFS-200 costs almost $1,000), but manufacturers expect that to
change over the next year or two.
The quality of home computer displays has
traditionally been limited by the most common type of display device,
the living room TV. But as video technology improves, and prices drop,
we can look forward to a new generation of home computers with the kind
of highresolution graphics and sharp 80-column text found today only on
the most expensive high-end computers.